1. Field of the Invention
The technical area of the present invention is that of external orthopedic devices designed to immobilize fractured limbs and reduce fractures. These types of devices are used for osteosynthesis with an external fixation device.
Treatment of fractures that are open, dirty, have large openings, are old, or caused by projectiles with high kinetic energies require external fixation. The fixation of a fracture, particularly an open fracture, must be stable, because compression, traction, twisting, and flexing stresses at the site of the fracture are transmitted to the external fixation device through the bone-pin connection. Rigidity of the fixation device is hence of the utmost importance in consolidating the bone fragments of a fracture. There are numerous external fixation devices of different typesxe2x80x94unilateral, frame, or circularxe2x80x94on the market.
The majority of operations with fixation devices performed on an emergency basis, particularly by field surgery under wartime or disaster conditions, usually have to be repeated because of reduction defects. Perfect initial surgery is rare.
There are only two options for the subsequent procedure:
remove the pins, re-perform the reduction, and reinsert the pins through a new connecting bar, thereby losing the value of the initial fixation;
leave the pins in place, and reduce by changing the assembly with two short bars (upper and lower) joined by a connecting means, whereby the assembly loses its initial rigidity.
2. Description of Related Art
External fixation devices composed of rigid tubes or equivalent means in which the pins engage and are held by screws are described for example in patents FR 2,442,044, FR 2,551,650, and FR 2,553,994.
In particular, Patent 2,457,656 describes a unilateral type fixation device for reducing a fracture comprising a main tube supporting two tube segments joined to the first with spherical mounts. Collars allow the two segments to slide relative to the main tube, and each tube has, in two mutually perpendicular planes, diametrically opposite, regularly spaced, threaded holes to receive the pins and the locking screws.
These fixation devices, worn by ambulant patients, have numerous drawbacks.
For instance, insertion on an emergency basis requires reduction and provisional containment of the bone site, or at least correct alignment of the limb if bone substance has been lost, before the pins are inserted. This constraint is the reason for many imperfect initial insertions.
In addition, the spacing of the pins is strictly defined by the holes in the tubes wherein the pins are located in a single plane and parallel to each other. This prevents flexibility in orienting or spacing the pins implanted in the bone.
Further, an apparatus having a large number of component parts, each having different diameters, develops to include a main tube, a tube segment, a spherical mount, a collar, and a pin. The large number of parts makes assembly difficult and is time-consuming when the surgeon is unaccustomed to their use.
Moreover, the various basic parts are not radiotransparent and are heavy because they are made of metal. The latter point is a drawback not only for the patient but also for field surgical teams carrying instrument kits.
U.S. Pat. No. 4,483,334 describes an external fixation device for fractures having pins screwed into the bone on either side of the fracture, a pair of rods connected to these pins on either side of the fracture, and a bridge connecting the rods with each other. The connecting mechanisms connecting each pin to the rods consist of a one-piece U-shaped assembly clamped to the pins, and a collar that is adapted to the diameter of the rods. The pins, rod, pin assemblies, and collars are held together by a single screw ensuring holding in all directions.
German Utility Model DE 91 03 480 describes a device for immobilizing a finger or a hand in the event of a fracture consisting of spikes screwed on either side of the fracture that are held together by a connecting rod. The connecting mechanism between the spikes and the connecting rod is comprised of a U-shaped collar, a socket, a screw provided with a hole for the spike to pass through, and a nut. When the nut is tightened, the spike is locked.
These two devices enable only one pin to be fixed by a connecting mechanism.
German Patent DE 295 12 917 describes an orthopedic device having a pin assembly for simultaneously holding at least two pins in parallel.
This assembly is composed of two identical parts forming a clamp. The clamp has depressions on two opposing faces for gripping and holding the pins.
This assembly has the drawback of holding only one pin diameter. In other words there is one type of assembly for each pin diameter. Thus, assemblies of different configurations must be available in order to achieve the immobilization desired.
Other orthopedic options are available that are lighter than the foregoing, and are made of radiotransparent and non-magnetic materials. An example of such is the fixation device described in French Patent FR 2,688,685. This device has a solid, rigid rod having transverse orifices for passage of pins screwed into the bone. These pins are fastened to the rod by fixation inserts or tightening collars. However, the spacing of the orifices, and hence the spacing of the pins, is strictly defined and invariable.
One goal of the present invention is to provide an external orthopedic fixation device compatible with existing fixation devices, particularly those used by the member countries of the North Atlantic Treaty Organization (NATO), for precise reduction of fractures by precise adjustments with several degrees of freedom.
Another goal of the present invention is to provide an orthopedic device that simplifies the installation of material by a non-specialist surgeon, thereby offering the opportunity to correct axial defects without modifying the pins in place, or requiring additional epiphyseal holding devices.
The further goal of the present invention is to provide an external fixation device having good rigidity and simultaneously:
simplifying the repositioning of axial defects without modifying the pins in place;
providing compatibility with the pins of employed with various fixation devices already in use, such as those employed in NATO countries;
enabling the use of the device by a non-specialist because the number of component parts is very small;
causing the reduction of fractures with the fixation device in place;
allowing muscle flaps to be created to cover the limbs involved by using a single-plane or at least unilateral assembly;
exploring an extremely simple design of the epiphyseal holding devices;
using self-drilling and self-tapping pins of different diameters for adaptation the various types of surgery;
more easily monitoring bone consolidation by x-ray or magnetic resonance imaging due to total radiotransparency of the device;
adding comfort to the patient because the implants are light.
For this purpose, the monolateral orthopedic device with external fixing for immobilizing a fractured bone has, in known fashion, a rigid support disposed parallel to the bone, at least two pins screwed into the bone and joined to the rigid support by a connecting mechanism comprising a pin-holding device composed of two identical parts forming a clamp whose two opposite faces have depressions. This device is characterized in that the depressions are able to receive and hold pins with diameters from 3 to 6 mm.
Preferably, the depressions of the device have different directions, i.e., the depressions in one of the directions enable pins 3 or 4 mm in diameter and parallel with each other to be held, and the depressions in the other direction, perpendicular to the previous direction, enable pins 5 or 6 mm in diameter and parallel with each other to be held.
Preferably, the connecting mechanism comprises a collar that can slide around the support and a single removable screw providing omnidirectional locking of each connecting mechanism and each pin relative to the support and its corresponding pin-holding device.
The pin-holding device can have a foolproofing mechanism, whereby the two identical clamp-forming parts each have a peg and a tongue accommodated in an orifice and a notch respectively of the other identical part. This mechanism makes it possible to guide one of the two parts relative to the other without hesitation.
Preferably, the device has means of assembling the pin-holding devices to the collars. These means can be crenellated surfaces made in each face to contact with the pin-holding devices and with each collar. This ensures precise indexing, cohesion of the parts with each other, and full immobilization of the pins relative to the rigid support.
Preferably, the collars, made of a flexible material, are clipped onto the rigid support and the transverse support. They may have a spacer to maintain a constant distance between the two ends of the collar and limit the torque of the screw.
Preferably, the rigid support is comprised of a cylindrical tube made of carbon.
Preferably, the entire device, with the exception of the pins, is made of a radiotransparent, non-magnetic material.
According to one embodiment, the device can have a transverse support joined to a rigid support by a collar to hold an epiphysis of the fractured bone using at least one pin screwed into the epiphysis and a connecting mechanism mounted on the transverse support.
The various types of parts in the device can have different colors to facilitate their identification when the device is mounted on the patient.
This device has the advantage of having a very small number of parts. The minimizing of parts saves a great deal of time and facilitates assembly of the device, both of which are essential in emergency surgery by an inexperienced surgeon.
Another advantage is that the support/collar and collar/pin-holding device connections allow the pins to move in all directions so that the device can be adapted when correcting alignment defects without modifying pins already in place.
Because the material is a light weight carbeon-type synthetic material, the consolidation x-rays are easy to read and the device is easy for the surgeon or patient to carry.
Another advantage is that the two types of pin-holding devices are fully compatible with the various pins already used this type of operation.
Other characteristics and advantages of the invention will emerge from the detailed nonlimiting description provided below.
The description below refers to the attached drawings that represent, without being limiting in nature, one embodiment of an orthopedic device with external fixing according to the present invention.